A fuel-cell vehicle is know that travels by supplying electric power generated by a fuel-cell system to a motor for driving the wheels of the vehicle. In the fuel-cell system, a fuel-cell stack (hereunder referred to simply as “a fuel cell”) generates electric power through a chemical reaction between hydrogen as a fuel gas and oxygen as a reactive gas. Here, the oxygen is taken in from the air via a compressor and the hydrogen is supplied from a high-pressure fuel gas container.
Meanwhile, the chemical reaction generates heat in a fuel-cell and in order to generate electric power efficiently, it is necessary to cool the fuel cell by dissipating excessive heat and to keep the fuel cell within an appropriate temperature range. In order to dissipate heat efficiently, it is only necessary to cool a fuel cell by using a water-cooling type cooling system and to dissipate the heat of the warmed cooling water with a radiator, for example as a fuel-cell vehicle shown in JP-A No. 192639/1996.
In a water cooling system generally used, a pipe line is connected to a heater to be cooled and a radiator so that cooling water may circulate in between and the cooling water is circulated by a pump disposed in the middle of the pipe line. Here, in some cases, a cooling fan to send air to the fins of the radiator is disposed in order to improve the heat dissipation efficiency of the radiator.
Meanwhile, as a means for driving a pump, an electric driving means that uses a built-in motor can be named. However, there is a concern in such an electric pump that the motor generates heat, thereby the efficiencies of the motor and the electric pump itself are lowered. This results in the efficiency of the cooling system being lowered. It is conceivable to cool the motor by introducing the circulated cooling water into the motor portion of the electric pump, but if such a means is applied, a more complex piping structure is required and also the thermal load of the cooling system increases.